The present invention relates to method and apparatus for performing wet clean, dry clean, vacuum heat drying, and vacuum freeze drying in one process without using a vacuum system, and capable of recovering low-pressure gas used in dry clean, and recovering cleaning solution and waste solution to achieve environment protection and energy saving. The apparatus includes at least one drain-to-vacuum apparatus, at least one vacuum vessel produced from the drain-to-vacuum apparatus, at least one heat control unit for vaporizing or sublimating cleaning solution, at least one heat egress unit for condensing vapors of the cleaning solution, and other auxiliary instruments, including a plurality of connection pipes. A low-dissolved-air cleaning solution is used and a drain-to-vacuum process is performed on the drain-to-vacuum apparatus, such that a cleaning vessel, which is not fully filled with the cleansing solution, becomes a vacuum vessel having very low internal air pressure and vapor pressure from the cleaning solution, enabling a minimized influence of any air pressure on any operation performed on the cleaning and vacuum drying apparatus. The present invention employs physical features that boiling points of general liquids lower with reduced pressure, that liquid saturated vapor pressure reduces with lowered temperature, and that two vacuum vessels of different working temperatures would have a pressure differential between their saturated vapor pressures, so that the enclosed cleaning vessel in a sealed state can be directly used to perform vacuum heat drying or vacuum freeze drying after dry and wet cleans have been completed therein. Therefore, wet clean, dry clean, vacuum heat drying, and vacuum freeze drying can be completed in one process, and low-pressure gas used in dry clean and cleaning solution and waste solution can be recovered to achieve environment protection and energy saving.
In a general cleaning and drying process, there is usually provided one or multiple clean working vessels, at where a workpiece is cleaned before being transferred to a next work platform for drying. For a finished product subject to heat deterioration, vacuum drying is particularly needed. When a cleaned finished product is moved in and exposed to atmosphere, it would be contaminated by particles again. Thus, it is desirable to develop a method to complete cleaning and vacuum drying of a workpiece in the same one cleaning vessel without the need of using an expensive vacuum system and to largely reduce related manufacturing costs.
It is a common practice in a cleaning process to use chemical solutions to clean off residual substances on the workpiece surface, such as particles, oxides, metal impurities, oil films, etc. It is possible that hazardous substances leak due to vaporization during the cleaning process. Such hazardous substances tend to explode and cause fires, resulting in serious damages and losses and adversely affecting operators"" health. Therefore, a cleaning system using enclosed vessels has advantages of reduced consumption of chemical solutions and pure water, and reduced emission of waste gases and reduced draining of waste water, as compared with a conventional open cleaning system.
In a known cleaning process using enclosed vessels, an amount of cleaning solution is introduced into an enclosed cleaning vessel that is sealed in a predetermined manner, and auxiliary equipment of the cleaning vessel removes contaminants from the surface of the workpiece. After the cleaning is completed, the cleaning solution is drained and the cleaned workpiece is removed from the cleaning vessel and transferred to another work platform for drying.
In a known dry clean process, a vacuum system is employed to draw air out of the cleaning vessel to produce vacuum therein. Thereafter, a type of gas is introduced into the vessel to chemically react with the workpiece to be cleaned, so that oxides on the surface of the workpiece are reduced. The cleaning gas is then drawn, and the workpiece is washed with pure water to create very clean, particle-free surface having a layer of natural oxide film. However, the use of vacuum system considerably increases the cleaning cost.
In a known vacuum heat drying process, a vacuum pump is employed to draw a working vessel to produce proper degree of vacuum therein. The vacuumized working vessel is then heated at a low temperature, so that moisture and volatile matters in the workpiece to be dried vaporize into vapors that are drawn out with the vacuum pump to dry the workpiece. To protect equipment included in the vacuum system from too much heat and vapors produced during heating and vaporization, it is necessary to install refrigerant compressor system and other equipment on the working vessel leading the vacuum pump, so as to condense the gaseous vapors into liquid water. This prevents the existing vacuum heat drying process from being a good design.
In a known vacuum freeze drying process, a workpiece to be dried is first frozen until moisture in the workpiece is frozen into solid state. Thereafter, a vacuum drying vessel is drawn to produce vacuum and reduce internal pressure thereof, so that the solid-state water in the workpiece to be dried is sublimated and drawn to produce vacuum in the drying vessel. This process is disadvantageous because it uses a refrigerant compressor to freeze the workpiece to be dried and uses a vacuum pump to draw the vacuum drying vessel to produce vacuum therein at the same time. At this stage, liquid water in the workpiece to be dried has not yet been frozen into the solid state, and gas drawn out of the vacuum system contains saturated vapors from the vaporized liquid water. The saturated vapors tend to condense into drops in the vacuum system to damage parts and components thereof. Although it is possible to install a freezing system before the vacuum pump to freeze the saturated vapors contained in the air drawn out of the vacuum drying vessel, the drying cost would increase accordingly. Therefore, the existing vacuum freeze drying process is not a perfect design.
With the existing processes, cleaning operation and vacuum drying operation are separately conducted in different working environments. Therefore, a workpiece or a product could not be cleaned and vacuum dried in the same one cleaning vessel, resulting in largely increased operating cost and considerable inconvenience in handling the cleaning and vacuum drying operations.
It is therefore tried by the inventor to develop improved method and apparatus for performing multiple cleaning and vacuum drying operations to eliminated is advantages existing in the above-mentioned conventional cleaning and vacuum drying techniques.
A primary object of the present invention is to provide cleaning and vacuum drying method and apparatus for performing multiple operations of wet clean, dry clean, vacuum heat drying, and vacuum freeze drying in enclosed vessels in one process without using a vacuum system, and capable of recovering low-pressure gas used in the dry clean and recovering cleaning solution and waste solution to achieve environment protection and energy saving.
The cleaning and vacuum drying apparatus of the present invention includes at least one drain-to-vacuum apparatus, at least one vacuum vessel created via the drain-to-vacuum apparatus, at least one heat control unit for vaporizing or sublimating the cleaning solution, at least one heat egress unit for condensing vapors, and other auxiliary apparatus, such as connecting pipes. The heat control unit vaporizes or sublimates the liquid or solid-state cleaning solution in the vacuumized cleaning vessel, and the heat egress unit condenses the gaseous cleaning solution in the vacuumized cleaning vessel into liquid or solid-state cleaning solution. The drain-to-vacuum apparatus uses low-dissolved-air cleaning solution and a drain-to-vacuum process to produce vacuum in the cleaning vessel, so that the cleaning vessel becomes a vacuum vessel having very low internal air pressure and vapor pressure from the cleaning solution to minimize the influence of air pressure on the whole process. Meanwhile, the present invention uses the physical features that boiling points of general liquids lower with reduced pressure, that liquid saturated vapor pressure reduces with lowered temperature, and that two vacuum vessels of different working temperatures would have a pressure differential between their saturated vapor pressures, and uses heat control unit and heat egress unit to regulate temperature and vapor pressure inside the vacuumized cleaning vessel, so that the heat control unit may introduce low-temperature heat energy or waste heat for the cleaning solution left on a workpiece to absorb heat of vaporization and be vaporized into gas. With these arrangements, dry and wet cleans, vacuum heat drying, and vacuum freeze drying can be completed within the same one cleaning vessel; and the recovery of low-pressure gas used in dry clean and the recovery of cleaning solution and waste solution can also be achieved.
Another object of the present invention is to provide cleaning and vacuum drying method and apparatus that increases the degree of vacuum of cleaning vessel by using a general drawing pump to reduce the pressure in a sealed lower vessel instead of using a vacuum system. When vacuum has been produced in the cleaning vessel, the cleaning vessel becomes a vacuumized cleaning vessel having very low internal air pressure and vapor pressure produced by the cleaning solution in the cleaning vessel. Therefore, the influence of air pressure on vacuum heat drying and vacuum freeze drying is minimized to effectively reduce costs of the cleaning and drying process.
The present invention relates to cleaning and vacuum drying method and apparatus for performing multiple operations of wet clean, dry clean, vacuum heat drying, and vacuum freeze drying in enclosed vessels in one process without using a vacuum system, and capable of recovering low-pressure gas used in the dry clean and recovering cleaning solution and waste solution to achieve environment protection and energy saving.
The cleaning and vacuum drying apparatus of the present invention includes at least one drain-to-vacuum apparatus, at least one vacuum vessel created via the drain-to-vacuum apparatus, at least one heat control unit for vaporizing or sublimating the cleaning solution, at least one heat egress unit for condensing vapors, and other auxiliary apparatus, such as connecting pipes. The heat control unit vaporizes or sublimates the liquid or solid-state cleaning solution in the vacuumized cleaning vessel, and the heat egress unit condenses the gaseous cleaning solution in the vacuumized cleaning vessel into liquid or solid-state cleaning solution. The drain-to-vacuum apparatus employs the principle that a liquid height is maintain under pressure to drain the cleaning solution in the cleaning vessel, so that the cleaning vessel becomes a vacuum vessel having very low internal air pressure and vapor pressure from the cleaning solution. The very low internal air pressure exists because air dissolved in the cleaning solution diffuses through vacuumized volume in the cleaning vessel when the liquid is drained from the enclosed cleaning vessel to produce vacuum therein. Therefore, the use of such low-dissolved-air cleaning solution as the cleaning solution in the drain-to-vacuum process is helpful in minimizing the influence of air pressure on the whole process. Meanwhile, the present invention uses the physical features that boiling points of general liquids lower with reduced pressure, that liquid saturated vapor pressure reduces with lowered temperature, and that two vacuum vessels of different working temperatures would have a pressure differential between their saturated vapor pressures, and uses heat control unit and heat egress unit to regulate temperature and vapor pressure inside the vacuumized cleaning vessel, so that the heat control unit may introduce low-temperature heat energy or waste heat for the cleaning solution left on a workpiece to absorb heat of vaporization and be vaporized into gas. With these arrangements, dry and wet cleans, vacuum heat drying, and vacuum freeze drying can be completed within the same one cleaning vessel; and the recovery of low-pressure gas used in dry clean, the producing of medium vacuum vessels, and the recovery of cleaning solution and waste solution can also be done to achieve environment protection and energy saving.
In brief, by using the low-dissolved-air cleaning solution and the drain-to-vacuum process on the cleaning and vacuum drying apparatus of the present invention, operations of 1) wet clean and vacuum heat drying, 2) wet clean and vacuum freeze drying, and 3) wet and dry cleans can be linked to perform on the same one apparatus; and, by using heat control unit and heat egress unit, operations of 4) vacuum heat drying, 5) vacuum freeze drying, 6) recovering cleaning solution and waste solution, and 7) producing a vessel of medium vacuum to recover the low-pressure gas used in the dry clean can be continued directly on the same apparatus.
Cleaning and Vacuum Drying Apparatus
The cleaning and vacuum drying apparatus of the present invention includes at least one drain-to-vacuum apparatus, at least one vacuum vessel created via the drain-to-vacuum apparatus, at least one heat control unit for vaporizing or sublimating the cleaning solution, at least one heat egress unit for condensing vapors, and other auxiliary apparatus, such as connecting pipes. Wherein, a cleaning vessel included in the cleaning and vacuum drying apparatus 1) may be separated from the drain-to-vacuum apparatus to serve as an independent vacuum vessels; 2) may serve as a vessel for dry clean, wet clean, vacuum heat drying, vacuum freeze drying, recovering cleaning solution and waste solution; 3) may be equipped at proper positions with other auxiliary equipment, such as heat control unit and heat egress unit, depending on actual needs; 4) may be connected to the vacuum vessels through connection pipes; 5) may be connected to a recovery container having normal internal pressure; and 6) may be connected to a cleaning vessel included in another drain-to-vacuum apparatus. With a saturated vapor pressure differential due to a temperature difference between the vacuumized cleaning vessel and the vacuum vessel, the solution in the vacuumized cleaning vessel is caused to absorb heat of vaporization and produce vapors that flow toward the vacuum vessels. The heat egress units are provided on the connection pipes between the vacuumized cleaning vessels and the vacuum vessels at proper positions to condense gaseous cleaning solution into liquid cleaning solution that is then recovered and stored in the vacuum vessels. The vacuum vessels may also be used to recover low-pressure gas used in the dry clean. In performing the operations of vacuum heat drying, recovering cleaning solution or waste solution, using low-dissolved-air cleaning solution, and producing medium vacuum vessels, the heat control unit provides a temperature range on a gas-liquid equilibrium curve of the cleaning solution. And, in performing the operation of vacuum freeze drying, the heat control unit and the heat egress unit provide temperature ranges on a gas-solid equilibrium curve of the cleaning solution.
When the cleaning and vacuum drying apparatus includes a plurality of cleaning vessels, these cleaning vessels can be interconnected by means of vacuum valves, and workpieces can be transferred among these cleaning vessels by means of conveyers, so that a serial multi-vessel cleaning and vacuum drying apparatus is provided.
Drain-to-Vacuum Apparatus
The drain-to-vacuum apparatus provides a link pipe having valve control function. The link pipe is connected at two ends to a cleaning vessel and a lower vessel that have a relative height difference between them. Both the cleaning vessel and the lower vessel are enclosed vessels and can be sealed in a predetermined manner. The lower vessel can be sealed and has increased volume and liquid surface cross-section area. The lower vessel is not fully filled with the cleaning solution, and has internal pressure that is set according to many factors, including the relative height difference between the cleaning vessel and the lower vessel, the specific gravity of the cleaning solution used in the cleaning and drying operations, the volume of the cleaning vessel, and the volume of the lower vessel. For the cleaning solution in the cleaning vessel to be completely drained into the lower vessel when the cleaning solution has very low specific gravity and the relative height difference between the cleaning vessel and the lower vessel is very small, the lower vessel usually has internal pressure that is much lower than the atmospheric pressure. The lower vessel is connected to a drawing pump for drawing the cleaning solution out of the lower vessel into a recovery container having normal internal pressure or a rear treatment vessel. When the lower vessel is in a sealed state, starting the drawing pump will cause the internal pressure of the lower vessel to reduce with the lowered liquid level in the lower vessel.
Drain-to-Vacuum Process
The drain-to-vacuum process of the present invention is based on the Torricelli vacuum producing principle, namely, a liquid level is maintained under pressure. The lower vessel has internal pressure that is set according to the relative height difference between the cleaning vessel and the lower vessel, the specific gravity of the cleaning solution, the volume of the cleaning vessel, and the volume of the lower vessel, and is regulated by means of the drawing pump. After the cleaning vessel is fully filled with the cleaning solution and then sealed, and a valve on the link pipe is opened, the cleaning solution in the cleaning vessel flows through the link pipe into the sealed lower vessel, and the pressure in the sealed lower vessel rises with the increasing cleaning solution. When the cleaning solution stops flowing, a still height thereof is the height of the cleaning solution that could be maintained by final liquid surface pressure in the sealed lower vessel 31. Thereafter, the valve on the link pipe is closed and the drawing pump is started again to draw the cleaning solution out of the sealed lower vessel into the recovery container or the rear treatment vessel. Meanwhile, the internal pressure of the sealed lower vessel is regulated to facilitate next cycle of the operation. Repeat the above procedures, until the still height of the cleaning solution at where the cleaning solution stops flowing reaches an actually required height.
Linked Wet Clean and Vacuum Heat Drying
When the cleaning and vacuum drying apparatus of the present invention is set for the operation of wet clean, the low-dissolved-air cleaning solution and the drain-to-vacuum process are used to produce vacuum in the cleaning vessel depending on actual needs. The vacuumized cleaning vessel is then used to perform the operation of vacuum heat drying, so that any residual moisture or organic solvent in the cleaning vessel is vaporized and recovered to the vacuum vessel, and the cleaned and dried workpiece is free of water mark and contamination by particles.
Linked Wet Clean and Vacuum Freeze Drying
The low-dissolved-air cleaning solution and the drain-to-vacuum process are used on the cleaning and vacuum drying apparatus of the present invention to produce vacuum in the cleaning vessel, so that the vacuumized cleaning vessel may be directly used to perform the next operation of vacuum freeze drying. Thus, the operations of wet clean and vacuum freeze drying could be performed in one process without using a vacuum system.
Linked Wet Clean and Dry Clean
After vacuum is produced in the cleaning vessel of the cleaning and vacuum drying apparatus of the present invention through the drain-to-vacuum process, a valve connecting the vacuumized cleaning vessel and a gas vessel for the dry clean operation is opened for cleaning gas in the gas vessel to flow into the vacuumized cleaning vessel via a connection pipe. The valve is then timely closed for the vacuumized cleaning vessel to have low gas pressure therein. After the dry clean is completed, a valve connecting the cleaning vessel and the vacuum vessel is opened, and the cleaning solution is introduced into the cleaning vessel via a bottom side thereof. While the liquid level in the cleaning vessel rises, the low-pressure cleaning gas is gradually recovered and stored in the vacuum vessel. After the cleaning vessel is completely filled with the cleaning solution, the valve connecting the cleaning vessel to the vacuum vessel is closed to complete the recovery of the low-pressure gas used in the dry clean.
Low-Dissolved-Air Cleaning Solution
When the drain-to-vacuum process is used on the cleaning and vacuum drying apparatus of the present invention to produce vacuum in a part of volume of the cleaning vessel, the liquid level of the cleaning solution becomes still in the cleaning vessel and covers the heat control unit provided in the cleaning vessel. When heat energy is continuously introduced into the cleaning solution, the liquid surface of the cleaning solution becomes boiled. At this point, air dissolved in the cleaning solution diffuses into the vacuumized volume of the cleaning vessel. The cleaning vessel is now in a normal pressure state, and the recovery container having normal internal pressure is used to collect from the cleaning vessel the air-diffused cleaning solution.
The temperature range of the heat control unit is on the gas-liquid equilibrium curve of the cleaning solution. Since the boiling point of the cleaning solution lowers with the reduced pressure in the cleaning vessel, the present invention may introduce low-temperature heat energy or waste heat to vaporize the cleaning solution. The cleaning vessel may be a vessel having a large cross-section area at the liquid surface in order to provide an increased vaporization area.
Vacuum Heat Drying
When the drain-to-vacuum process is implemented on the cleaning and vacuum drying apparatus of the present invention, the cleaning vessel can become a vacuumized cleaning vessel having very low internal air pressure and vapor pressure from the cleaning solution. Utilizing the principle that temperature difference results in saturated vapor pressure differential, the vacuum vessel is connected to the cleaning vessel, and the heat egress unit is mounted at a proper position on the connection pipe between the cleaning vessel and the vacuum vessel to condense the gaseous cleaning solution flowing toward the vacuum vessel into liquid that is then recovered and stored in the vacuum vessel.
The heat control unit of the cleaning vessel provides heat of vaporization to vaporize the cleaning solution left on the workpiece being cleaned. When the temperature of the heat control unit keeps unchanged and the internal pressure of the cleaning vessel does not change any longer, it means the temperature and the internal pressure of the cleaning vessel are on the gas-liquid equilibrium curve of the cleaning solution. If the internal pressure of the cleaning vessel does not reach the saturated vapor pressure at that temperature, the workpiece to be dried could absorb the heat of vaporization from the heat control unit to vaporize the cleaning solution left on the workpiece. To continuously vaporize the cleaning solution left on the workpiece to be dried, the above-mentioned principle of pressure differential is utilized to drive vapors to flow toward the heat egress unit on the connection pipe connected to the vacuum vessel, so that the gaseous cleaning solution is condensed into liquid and then recovered and stored in the vacuum vessel. In this manner, the internal pressure of the cleaning vessel is always maintained lower than the saturated vapor pressure at the vaporization temperature. Since general liquid has a boiling point that lowers with reduced pressure, the heat control unit may introduce low-temperature heat energy or waste heat to vaporize the cleaning solution.
When the low-dissolved-air cleaning solution is used as the cleaning solution in the drain-to-vacuum process, the operation of vacuum heat drying is not influenced by the air pressure, enabling a more stable pressure differential between the vacuum vessel and the vacuumized cleaning vessel and the use of heat energy of lower temperature.
Vacuum Freeze Drying
By using the low-dissolved-air cleaning solution and the drain-to-vacuum process on the cleaning and vacuum drying apparatus of the present invention, vacuum can be produced in the cleaning vessel for the same to become a vacuumized cleaning vessel having very low internal air pressure and vapor pressure from the cleaning solution. The heat control unit and the heat egress unit of the cleaning vessel provide temperature ranges are on the gas-solid equilibrium curve of the cleaning solution. The heat control unit controls the temperature of the workpiece to be dried. That is, the heat control unit is able to lower the temperature of the workpiece to be dried to a preset temperature and provides heat of sublimation to sublimate solid-state cleaning solution inside the workpiece. The heat egress unit controls the pressure inside the vacuumized cleaning vessel. That is, the heat egress unit is able to condense the sublimated cleaning solution into solid-state cleaning solution and to provide heat of sublimation to sublimate the solid-state cleaning solution left in the vacuumized cleaning vessel.
In the course of vacuum freeze drying a workpiece to be dried in the cleaning vessel, when the temperature of the heat control unit in the cleaning vessel keeps unchanged and a rate of sublimation equal to a rate of condensation, the internal pressure of the cleaning vessel would not change any longer. That is, the temperature and the internal pressure of the cleaning vessel are on the gas-solid equilibrium curve of the cleaning solution. When the heat control unit is at the sublimation temperature set for it, and if the pressure inside the cleaning vessel does not reach the saturated vapor pressure at that temperature, the workpiece to be dried could absorb the sublimation heat from the heat control unit to sublimate the solid-state cleaning solution on the workpiece to form the gaseous cleaning solution. To continue the sublimation while there is very low air pressure in the cleaning vessel, the heat egress unit is used to condense the previously sublimated cleaning solution into solid state, so that the internal pressure of the cleaning vessel is always maintained lower than the saturated vapor pressure at the sublimation temperature.
The heat control unit is able to freeze the workpiece to be dried to the lowest eutectic point of the compositions of the workpiece. In the course of freezing the workpiece to be dried with the heat control unit, it is necessary to prevent the internal pressure of the whole cleaning vessel from reducing with lowered temperature and resulting in incompletely frozen workpiece. Thus, the heat egress unit must vaporize or sublimate the cleaning solution left in the cleaning vessel for the internal vapor pressure of the cleaning vessel to be larger than the saturated vapor pressure at the temperature set for the heat control unit until the workpiece to be dried has been frozen to a temperature lower than its lowest eutectic point.
After the workpiece to be dried has been frozen, it is expected the liquid inside the workpiece has big crystal size to form eye-visible coarse crystals. The coarse crystals leave big voids in the workpiece after they have sublimated, allowing crystals at inner side of the workpiece to keep sublimating and therefore enabling an enhanced drying efficiency. Thus, the workpiece to be dried is pre-frozen under normal pressure and the low-dissolved-air cleaning solution and the drain-to-vacuum process are used to produce vacuum in the cleaning vessel before performing the vacuum freeze drying.
When the low-dissolved-air cleaning solution is used as the cleaning solution in the drain-to-vacuum process, there will be only the vapor pressure from the cleaning solution existing in the vacuumized cleaning vessel. Thus, the operation of vacuum freeze drying is not affected by the air pressure, and both the sublimation and the condensation of the cleaning solution inside the workpiece to be dried are controlled by temperature. In the case the heat egress unit includes means for speeding up the flowing of the gaseous cleaning solution, the gaseous cleaning solution could condense into solid state more quickly to increase the rate of vacuum freeze drying.
Serial Multi-Vessel Vacuum Freeze Drying
In the serial multi-vessel cleaning and vacuum drying apparatus of the present invention, the heat control unit in the first cleaning vessel serves to pre-freeze the cleaned workpiece to be dried under normal pressure, the second cleaning vessel has an initial state in which the low-dissolved-air cleaning solution and the drain-to-vacuum process are used to produce vacuum in the cleaning vessel and serves as the cleaning vessel for performing the vacuum freeze drying, and the third cleaning vessel serves to output the workpiece that has been dried. After the third cleaning vessel is returned to normal internal pressure and the dried workpiece is removed therefrom, it is treated with the low-dissolved-air cleaning solution and the drain-to-vacuum process to become a vacuum vessel again. After the workpiece to be dried has been frozen, it is expected the liquid inside the workpiece has big crystal size to form eye-visible coarse crystals. The coarse crystals leave big voids in the workpiece after they have sublimated, allowing crystals at inner side of the workpiece to keep sublimating and therefore enabling an enhanced drying efficiency. Thus, the workpiece to be dried is pre-frozen under normal pressure and then subjected to vacuum freeze drying.
After the workpiece to be dried is cleaned in the first cleaning vessel, the heat control unit is actuated under normal pressure to pre-freeze the workpiece to be dried. Then, use low-temperature and low-dissolved-air cleaning solution and the drain-to-vacuum process to produce vacuum in the first cleaning vessel, open the vacuum valve and send the workpiece to be dried to the second vacuumized cleaning vessel, close the vacuum valve, lower the temperature of the workpiece to be dried below the eutectic point of the workpiece, and perform the vacuum freeze drying. After the vacuum freeze drying is completed, the vacuum valve is opened, the dried workpiece is sent to the third vacuumized cleaning vessel, and the vacuum valve is closed again. When the third cleaning vessel is returned to normal internal pressure, the dried workpiece is removed from the third cleaning vessel.
Recovering Cleaning Solution and Waste Solution
In the cleaning and vacuum drying apparatus of the present invention, a first cleaning vessel is used as a vaporization vessel for vaporizing the cleaning solution or waste solution, and a second cleaning vessel is used as a recovery vessel for recovering clean cleaning solution and waste solution. The vaporization vessel is provided with the heat control unit for supplying heat of vaporization to vaporize the cleaning solution or the waste solution. Since the temperature difference between the vaporization vessel and the recovery vessel results in a saturated vapor pressure differential, gaseous cleaning solution in the vaporization vessel is caused to flow toward the heat egress unit connected to the recovery vessel and be condensed into liquid that is recovered in the recovery vessel.
By using the cleaning solution or waste solution to be recovered and the drain-to-vacuum process, vacuum is produced in the vaporization vessel. The liquid level of the cleaning solution to be recovered becomes still in the vaporization vessel and covers the heat control unit. By using clean cleaning solution or waste solution and the drain-to-vacuum process, vacuum is produced in the recovery vessel. When the cleaning solution or waste solution in the vaporization vessel absorbs heat of vaporization from the heat control unit, and the heat egress unit condenses vapors produced in the vaporization vessel into clean liquid cleaning solution or solution that is recovered to the recovery vessel, the vaporization vessel may be timely replenished with the cleaning solution or waste solution, and the recovery vessel may timely drain the recovered cleaning solution or solution into a recovery container having normal internal pressure. Thereafter, the drain-to-vacuum process is implemented again to make the recovery vessel a vacuum vessel to continue the recovery of clean cleaning solution or solution. Since the boiling point of the cleaning solution or waste solution to be recovered lowers with the reduced pressure, the heat control unit may introduce low-temperature heat energy or waste heat to vaporize the cleaning solution or waste solution. In this manner, the object of environment protection and energy saving can be achieved.
Producing Medium Vacuum Vessel
On the cleaning and vacuum drying apparatus, the low-dissolved-air cleaning solution and the drain-to-vacuum process may be used to produce two vacuumized cleaning vessels, one of which may be detached from the drain-to-vacuum apparatus to serve as a vacuum vessel, and the other one of which is used to recover condensed liquid. Since the temperature difference between the two vessels results in a saturated vapor pressure differential, the liquid left in the vacuum vessel absorbs heat of vaporization to produce gaseous cleaning solution that flows toward the heat egress unit connected to the vacuumized cleaning vessel and be condensed into liquid cleaning solution, which is then recovered to the vacuumized cleaning vessel.
Since the boiling point of general liquid lowers with reduced pressure, the heat control unit may introduce low-temperature heat energy or waste heat to vaporize the cleaning solution left in the vacuum vessel. With the increasing temperature and reducing vapors in the vacuum vessel, the vacuum vessel finally contains only a very small amount of dry vapor therein. The vacuum vessel is then sealed and detached from the drain-to-vacuum apparatus, and the temperature thereof is lowered again. With lowered temperature, the vacuum vessel may become a vacuum vessel close to medium vacuum.